Effects of Layer Thickness and Annealing of PEDOT:PSS Layers in Organic Photodetectors

• Published in: Macromolecules Vol. 42; no. 17; pp. 6741 - 6747
• Main Authors: Friedel, Bettina, Keivanidis, Panagiotis E, Brenner, Thomas J. K, Abrusci, Agnese, McNeill, Christopher R, Friend, Richard H, Greenham, Neil C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08.09.2009
• Subjects: Application fields; Applied sciences; Energy; Exact sciences and technology; Natural energy; Photovoltaic conversion; Polymer industry, paints, wood; Solar cells. Photoelectrochemical cells; Solar energy; Technology of polymers; Ultrathin films; Annealing; Electrical properties; Aromatic polymer; Experimental study; Quantum yield; Layer thickness; Fill factor; Photodetector; Open circuit voltage; Photovoltaic cell; Conducting polymers; Thiophene derivative polymer; Ethylenedioxythiophene polymer; Thermal history; Styrenesulfonic acid polymer; Size effect; Electric resistivity; Doped polymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma901182u

We have investigated the effects of thickness variation and thermal treatment of the electrode polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) in photovoltaic and photodetector devices using conjugated polymer blends as the photoactive material. By variation of the PEDOT:PSS layer thickness between 25 and 150 nm, we found optimum device performance, in particular low dark current and high external quantum efficiency (EQE) and open-circuit voltage (V oc), at around 70 nm. This has been observed for two different active layers. Annealing studies on the PEDOT:PSS films, with temperatures varied between 120 and 400 °C, showed an optimum device performance, in particular EQE and V oc at 250 °C. This optimum performance was found to be associated with loss of water from the PSS shell of the PEDOT:PSS grains. For annealing temperatures above 260 °C, device performance was dramatically reduced. This was associated with chemical decomposition leading to loss of sulfonic acid, although this did not significantly affect the in-plane conductivity.